Back in July, at the iPhone 4 Antennagate conference, Steve Jobs acknowledged the iPhone 4's proximity sensor issues and said they'd be fixed in the "next update." According to an Apple Australia spokesperson, they won't.
We've been getting trouble reports from users about their iPhone 4, especially around the antenna reception/dropped calls issue. There are smaller factory defects as well, and thankfully they're not as widespread, which means you can exchange your phone.
You know how some capacitive touchscreens seem to twitch when fingers are hovered near them? Mitsubishi has stretched that ability to the extreme, creating a magic(ish) touch panel that can track depth, too.